DateTime2 vs DateTime in SQL Server

Question

Which one:

• datetime
• datetime2

is the recommended way to store date and time in SQL Server 2008+?

I\'m aware of differ

Answer 1

Here is an example that will show you the differences in storage size (bytes) and precision between smalldatetime, datetime, datetime2(0), and datetime2(7):

DECLARE @temp TABLE (
    sdt smalldatetime,
    dt datetime,
    dt20 datetime2(0),
    dt27 datetime2(7)
)

INSERT @temp
SELECT getdate(),getdate(),getdate(),getdate()

SELECT sdt,DATALENGTH(sdt) as sdt_bytes,
    dt,DATALENGTH(dt) as dt_bytes,
    dt20,DATALENGTH(dt20) as dt20_bytes,
    dt27, DATALENGTH(dt27) as dt27_bytes FROM @temp

which returns

sdt                  sdt_bytes  dt                       dt_bytes  dt20                 dt20_bytes  dt27                         dt27_bytes
-------------------  ---------  -----------------------  --------  -------------------  ----------  ---------------------------  ----------
2015-09-11 11:26:00  4          2015-09-11 11:25:42.417  8         2015-09-11 11:25:42  6           2015-09-11 11:25:42.4170000  8

So if I want to store information down to the second - but not to the millisecond - I can save 2 bytes each if I use datetime2(0) instead of datetime or datetime2(7).